Liquid fertilizer recovered from the effluent water of recirculating aquaculture system by reverse osmosis exhibits storage stability independent of pasteurization

The shift to a circular bioeconomy is dependent on green-tech innovations that upcycle waste streams into reusable components. The current study explores the chemical and microbiological stability of a fertilizer concentrate produced from effluent water of recirculating aquaculture systems (RAS) using reverse osmosis. The objective was to assess the shelf life of the concentrate and determine whether pasteurization is required to prevent spoilage during storage in light-proof containers at room temperature for six months. The chemical and microbiological storage stability of the pasteurized concentrate was monitored by periodic sampling and compared to an untreated control. Pasteurization decreased the initial concentration of elements dissolved in the concentrate, the viable cell load and the percentage of intact bacterial cells. However, both the pasteurized and the untreated control maintained chemical and microbiological stability during storage, indicating that the concentrate has a shelf life of at least 6 months independent of pasteurization. The concentrate is therefore suitable for long-term storage, without the increased production costs and energy use required for pasteurization, thereby providing a reliable and circular source of plant nutrients that have the potential to support sustainable farming practices. This study will contribute to the continued transition towards sustainable aquaculture by repurposing RAS effluent as a valuable by-product for crop cultivation.